<?php
/**
 * Nonce-related functionality.
 *
 * @package OpenID
 */

/**
 * Need CryptUtil to generate random strings.
 */
require_once 'Auth/OpenID/CryptUtil.php';

/**
 * This is the characters that the nonces are made from.
 */
define('Auth_OpenID_Nonce_CHRS', "abcdefghijklmnopqrstuvwxyz" . "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789");

// Keep nonces for five hours (allow five hours for the combination of
// request time and clock skew). This is probably way more than is
// necessary, but there is not much overhead in storing nonces.
global $Auth_OpenID_SKEW;
$Auth_OpenID_SKEW = 60 * 60 * 5;

define('Auth_OpenID_Nonce_REGEX', '/(\d{4})-(\d\d)-(\d\d)T(\d\d):(\d\d):(\d\d)Z(.*)/');

define('Auth_OpenID_Nonce_TIME_FMT', '%Y-%m-%dT%H:%M:%SZ');

function Auth_OpenID_splitNonce($nonce_string) {
  // Extract a timestamp from the given nonce string
  $result = preg_match(Auth_OpenID_Nonce_REGEX, $nonce_string, $matches);
  if ($result != 1 || count($matches) != 8) {
    return null;
  }
  
  list($unused, $tm_year, $tm_mon, $tm_mday, $tm_hour, $tm_min, $tm_sec, $uniquifier) = $matches;
  
  $timestamp = @gmmktime($tm_hour, $tm_min, $tm_sec, $tm_mon, $tm_mday, $tm_year);
  
  if ($timestamp === false || $timestamp < 0) {
    return null;
  }
  
  return array($timestamp, $uniquifier);
}

function Auth_OpenID_checkTimestamp($nonce_string, $allowed_skew = null, $now = null) {
  // Is the timestamp that is part of the specified nonce string
  // within the allowed clock-skew of the current time?
  global $Auth_OpenID_SKEW;
  
  if ($allowed_skew === null) {
    $allowed_skew = $Auth_OpenID_SKEW;
  }
  
  $parts = Auth_OpenID_splitNonce($nonce_string);
  if ($parts == null) {
    return false;
  }
  
  if ($now === null) {
    $now = time();
  }
  
  $stamp = $parts[0];
  
  // Time after which we should not use the nonce
  $past = $now - $allowed_skew;
  
  // Time that is too far in the future for us to allow
  $future = $now + $allowed_skew;
  
  // the stamp is not too far in the future and is not too far
  // in the past
  return (($past <= $stamp) && ($stamp <= $future));
}

function Auth_OpenID_mkNonce($when = null) {
  // Generate a nonce with the current timestamp
  $salt = Auth_OpenID_CryptUtil::randomString(6, Auth_OpenID_Nonce_CHRS);
  if ($when === null) {
    // It's safe to call time() with no arguments; it returns a
    // GMT unix timestamp on PHP 4 and PHP 5.  gmmktime() with no
    // args returns a local unix timestamp on PHP 4, so don't use
    // that.
    $when = time();
  }
  $time_str = gmstrftime(Auth_OpenID_Nonce_TIME_FMT, $when);
  return $time_str . $salt;
}
